A power system may comprise an internal combustion engine and an exhaust gas recirculation system (EGR system). The EGR system recirculates a portion of the engine's exhaust gas back into the engine's intake manifold. The recirculated exhaust gas that is recirculated reduces the concentration of oxygen therein, which then lowers the combustion temperature, slows the chemical reactions, and decreases the formation of nitrous oxides (NOx). Increased EGR rates of up to 50% may be necessary for meeting Tier 4 emissions standards. At such high rates, tremendous amounts of recirculated exhaust gas enter the intake manifold and increase the intake manifold temperature. The rising intake manifold temperature—as the result of what may be referred to as “warm EGR”—adversely affects the engine's power and emissions reduction potential.
Past power systems have used liquid cooled EGR coolers for cooling the “warm EGR,” rather than using ambient air. However, the use of liquid cooled EGR coolers is disadvantageous. The use of liquid cooled EGR coolers is inefficient, because heat transfers, from the “warm EGR,” to the engine coolant, and then the heat transfers, from the engine coolant, to ambient air. So, for example, if the engine coolant is at 95° C. and the ambient air is at 30° C., there is a small temperature differential of only 65° C. With such a small temperature differential, a tremendous amount of fan power is necessary for removing the heat from the “warm EGR.” This difficulty arises, because the temperature differential is the driving force for transferring heat.
A further problem associated with EGR coolers is the formation of condensation within themselves.
What is needed is a power system that cools the “warm EGR” without the use of liquid engine coolant, and with only minimal amounts of fan power. What is further needed is a power system that prevents the formation of condensation within the EGR coolers.